The present patent application describes detergents, in particular detergents for machine dishwashing. The present application in particular provides phosphate-free automatic dishwashing agents.
More stringent requirements are today often applied to machine washed dishes than are applied to hand washed dishes. For instance, after machine washing, dishes should not only be completely free of food residues but should for example also not exhibit any whitish blemishes based on water hardness or other mineral salts which originate from dried water drops due to a lack of wetting agents.
Modern automatic dishwashing agents satisfy these requirements by incorporating washing, conditioning, water softening and rinsing active ingredients and are for example known to the consumer as “2-in-1” or “3-in-1” dishwashing detergents. Automatic dishwashing agents intended for private consumers contain builders as an essential component for successful washing and rinsing. On the one hand, these builders increase the alkalinity of the washing liquor, fats and oils being emulsified and saponified as alkalinity rises, and, on the other hand, reduce the water hardness of the washing liquor by complexing the calcium ions present in the aqueous liquor. Alkali metal phosphates have proved to be particularly effective builders, for which reason they form the main ingredient of the majority of commercially obtainable automatic dishwashing agents.
While phosphates are thus very highly regarded in terms of their advantageous action as a component of automatic dishwashing agents, their use is, however, not entirely unproblematic from an environmental protection standpoint since a significant proportion of the phosphate passes with domestic wastewater into bodies of water and, especially in standing bodies of water (lakes, dams), plays a considerable part in their eutrophication or overfertilization. As a consequence of this phenomenon, the use of pentasodium triphosphate in textile detergents has been considerably reduced by statutory regulations in quite a number of countries, for example the USA, Canada, Italy, Sweden, Norway, and has been entirely prohibited in Switzerland. In Germany, since 1984, the permitted maximum content of this builder in laundry detergents has been 20%.
In addition to nitrilotriacetic acid, sodium aluminum silicates (zeolites) are primarily used as phosphate replacements or substitutes in textile detergents. However, for various reasons, these substances are not suitable for use in automatic dishwashing agents. A series of replacements have accordingly been discussed in the literature as alternatives to alkali metal phosphates in automatic dishwashing agents, among which citrates are of particular significance.
European patents EP 662 117 B1 (Henkel KGaA) and EP 692 020 B1 (Henkel KGaA), for example, describe phosphate-free automatic dishwashing agents which, in addition to a citrate, furthermore contain carbonates, bleaching agents and enzymes.
A further alternative to alkali metal phosphates, which as sole builder is however preferably used in combination with citrates, is methylglycinediacetic acid (MGDA). European patent EP 906 407 B1 (Reckitt Benckiser) or European patent application EP 1 113 070 A2 (Reckitt Benckiser), for example, describe MGDA-containing automatic dishwashing agents.
Despite the efforts so far made, manufacturers of automatic dishwashing agents have not hitherto managed to provide phosphate-free automatic dishwashing agents which are comparable to or even surpass phosphate-containing detergents with regard to their washing and rinsing performance and in particular also their performance in terms of film deposition inhibition. Such equality of performance is, however, a prerequisite for the successful market introduction of phosphate-free detergents, since the majority of end consumers, despite the widespread public discussion of environmental issues, will always decide against an environmentally advantageous product if this product is not in line with the market standard in terms of price and/or performance.